1. Field of the Invention
The present invention generally relates to bearings and, more particularly, to a geometric shaped side bearing pad.
2. Description of the Related Art
Rail cars are typically equipped with wheeled trucks including side bearings that are adapted, for example, to absorb energy in response to large impact loads, to control or restrict hunting movements of the rail cars, to decrease warping tendencies of the rail cars, to provide better curving characteristics of the rail cars, etc. Truck hunting occurs during movement of a rail car over tracks or rails and is caused mainly by worn wheels and/or worn rail. Truck hunting can lead to rapid truck component wear and can cause high speed derailments.
Side bearing developments to reduce or otherwise control adverse truck action have been ongoing for years. For example, side bearings have been developed with various types of springs, hydraulics dampers, yaw dampers, etc. Some side bearings use compressed resilient members, such as spring loaded members, elastomeric members, etc. Side bearing pads have normally been formed as straight cylinders or columns, toroids, or metal-rubber sandwich structures.
Side bearings have also used different forms of thermoplastic elastomers to absorb necessary forces encountered in railroad cars, and typically require special fixturing. U.S. Pat. Nos. 4,962,916, 6,419,214 B2, and 6,723,771 B2, issued Oct. 16, 1990, Jul. 16, 2002, and Apr. 20, 2004, respectively, to at least the present inventor, describe compression springs, non-linear spring rate sway bar bushings, and high friction polyurethane elastomers having improved abrasion resistance, and are incorporated herein by reference.
A side bearing pad having a spring rate that allows the storage of deflection energy while limiting reaction force is desirable.